1. Field of the Invention
The invention relates to a coupling for mill rolls, for use in the iron and steel industry to couple a roll with a cardan shaft.
2. Description of the Prior Art
It is known for the connection between the roll and a connecting member which transmits drive from a cardan shaft to be embodied as a mortise-and-tenon joint, secured against rotation. For this purpose, the roll is provided with a pin or projection and the connecting member with a hole or recess to receive the projection.
This type of coupling is used for slab rolls in slabbing mills and for roughing rolls and finishing rolls in hot strip mills. The drive for such heavy mill stands is supplied by an electric motor, the power of which after reduction in speed is split and led to two rolls by means of cardan shafts. The rolls are journalled in so-called chucks. During operation, the thickness of the rolled material in the gap between the two workrolls reduces, so that the chucks in the roll stand should be movable and in consequence the angle of the cardan shafts must be variable. The roll and the cardan shaft are coupled to each other by means of the connecting member.
Usually the connection between the roll and the connecting member is a mortise-and-tenon one, for which purpose the roll has a projection which fits with the least possible play into a hole in the connecting member. This play, however, is sufficient to allow the joint to be easily assembled and disassembled. This radial play required for assembly and disassembly is eliminated after assembly by means of a radial bolt. The connection can be secured against rotation by means of flats on the projection, corresponding key slots in the connecting member and feather keys (plate keys) in the keyways thus provided.
A problem arises in the operation of this known design of the connection between the workroll and the connecting member in that the connection is often damaged by the loads which arise during the heavy work which such rolls have to perform. The mortise and tenon have then to be repaired by welding the projection and spraying material into the hole and subsequent mechanical machining of both. This entails loss of production and high maintenance costs.